Editor’s Note: Stephen S. Schneck is director of the Institute for Policy Research and Catholic Studies at The Catholic University of America.

By Stephen S. Schneck, Special to CNN

For years, pollsters and political scientists have been stumped about Catholics.

On one hand, it’s been pretty clear that as American Catholics go, so goes the nation. George W. Bush narrowly won the Catholic vote in 2004 and won a second term. Barack Obama narrowly won the Catholic vote in 2008 and, with it, the White House.

It’s easy to see why Catholics are sometimes seen as the swing voters whose shifting political preferences swing elections.

Nevertheless, the idea of a Catholic bloc is patently ridiculous. As voters, American Catholics mirror the electorate as a whole, divided into Democrats, independents, and Republicans at about the same percentages as all Americans. And it’s hard to trace such political complexity to religious allegiance.

One explanation for why is the sheer number of Catholic voters and their now multigenerational assimilation into American society. About 35 million Catholics voted in 2008. That’s about 27% of all voters.

In the 19th century and for much of the 20th, Catholics self-consciously occupied a distinctive identity in America. Predominantly blue collar, they often lived in white ethnic neighborhoods, attended their own schools and colleges, established their own hospitals and charities, and experienced some level of discrimination.

In those years, Catholics associated overwhelmingly with the Democratic Party, which not only accommodated but promoted policies that advanced ethnic assimilation – everything from minimum wage laws to the GI Bill.

But by finally achieving that assimilation, Catholics in the last 50 years have lost much of their sense of special self-identity. For white Catholics, who are about 60% of the Catholic vote, their distinctiveness in class, education, income, and even ethnicity has grown increasingly ambiguous in America’s famous melting pot.

The melting pot has even transformed Catholics’ relationship to their church. Polling numbers released Friday by CNN about the White House contraception dust-up illustrate this: Only 11% of Catholics polled said they should always obey official church teachings on moral issues like birth control and abortion.

To put this differently, 88% of Catholics in the poll said that it’s OK for Catholics to make up their own minds about these moral issues. That represents a growing trend. In 1992 only 70% supported the “make up their own minds” argument. In 1999 it was 80%.

Today’s Catholics are picky and even suspicious about political signals from the institutional church.

Politically conservative Catholics bristle at do-gooder messaging from their bishops about climate change, immigration reform and Catholicism’s important “preferential option” for the poor. Politically liberal Catholics, meanwhile, are not much swayed by the righteous tone of church pronouncements about same-sex marriage and contraception.

And yet despite the pattern and consequences of assimilation, something Catholic is going on in politics. It’s evident when you drill down into the polling numbers. While there is not an obvious Catholic vote on the macro scale, there are three discrete "Catholic votes” that really matter in American elections.

The first of these is Latino Catholics.  Over the last three decades, Latino immigration has washed over the church in America like a flood.  From insignificant numbers 40 years ago, Latinos now constitute one-third of all American Catholics.

In the not-too-distant future, the majority of American Catholics will probably be Latinos.

Unlike the Italians, Poles, Irish and similar white ethnics, Latino Catholics have retained their distinctive identity as Catholics. Their voting behavior reflects that.

This is particularly true when considered from the perspective of the famous social teachings of the church, which emphasize social and familial solidarity, the common good, preference for the poor, tradition, and welcoming of the immigrant.

Latino American Catholics (excluding Cubans) strongly associated with the Democratic Party in 2008, with 67% of Latino Catholic voters supporting Obama. But the bloc includes swing voters, and turnout can be volatile. This vote can be critical in swing states like Colorado, Florida and New Mexico, and perhaps soon in states like Arizona and Texas.

A little deeper in the weeds are two other important groups of white Catholic voters, who might be called “intentional Catholics” and “cultural Catholics.”

An important social phenomenon for understanding intentional Catholics is what’s sometimes referred to as distillation. A study by the Pew Forum on Religion and Public Life last year found that one-third of those raised Catholic have left the church. Fully 10% of the American electorate is formerly Catholic.

Because of assimilation, the glue of tradition and culture that previously inclined many to adhere to the church has lost its stickiness. Leaving is easy, whether by decision or atrophy, and little shame results.

Such disaffiliation happens for liberal reasons, conservative reasons, personal reasons and no reason at all. Some who leave still feel lingering allegiance to things Catholic, but many do not, and former Catholics do not have a distinctive political identity.

But as a result of disaffiliation, many Catholics who remain with the church are “distilled.”  More and more of those who remain are those who actively choose to embrace the church and its teachings. These “intentional Catholics” are the second of the three important groups of Catholic voters.

Largely white, with impressive education levels, mostly suburban and with moderate to high income levels, such Catholics are in evidence in weekly Mass attendance and parish activities. Politically active, intentional Catholic voters lean toward the Republican Party (with some youthful swing voters) and are motivated by economic issues and increasingly by opposition to abortion, same-sex marriage and illegal immigration.

“Cultural Catholics” make up the third important group of Catholic voters. They are a complicated mix of mostly white Americans with lower levels of Mass attendance and higher levels of ambivalence toward Church authority.

These assimilated voters have varying education and income levels, often hail from urban and suburban communities, are more female than male – often with blue-collar roots – and are not intentionally but culturally oriented toward the church.

Because of the relative size of the Catholic population in battleground states like Pennsylvania, Ohio, Michigan and Wisconsin, swing voters in this group can be pivotal in presidential elections.

Many culturally Catholic voters are at odds with both conservatives and liberals on many issues. They are more socially conservative than the majority of Americans, but many are put off by the more intense social conservatism of intentional Catholics and evangelicals.

They are more economically populist than most Americans but are uncomfortable with the libertarian zeal of the tea party.  They are alienated from the lifestyle liberalism of many progressives but remain supportive of unions and governmental programs for the middle class.

The bishops may have little role in these voters’ personal faith, but cultural Catholics look to the church for the sacraments that mark the turnings of their lives and for the traditions that connect generations. Their religious sensibility might almost be described as ethnic.

Neither Obama nor any of the Republican candidates has clinched the deal for the voters in this group. Whoever does will probably win in November.

The opinions expressed in this commentary are solely those of Stephen S. Schneck